Found an exploit. Go play in the 1st stage and don't skip the tutorial, go afk for as long as you like. Once you come back you see many boxes lying around the field. Open the boxes and you can get many Unit and Money.
Also, you should add the chat box if the player enters or left the game.Because you don't even know if a player leaves or joining, and its going to be a little annoying that you walking around finding the enemy and you check the score and your the only player who is playing the map.
If you have low life or getting annoyed by a zombie hored you can take out the game and put it back to your safe file and when it load there are no zombies and get less annoyed or safe
So game is good it works your mind (better than a puzzle games that i played) so i like the combo for each of it is depend that is challenge to collect every star from the game so 5/5 make more good puzzle games
currently there are a lot of weapons, (over 10), but I can add more weapons in the future